Container for blood and machine for separating precipitates from liquid blood constituents



July 2., 1963 G. N. HEIN 3,096,283

CONTAINER FOR BLOOD AND MACHINE FOR SEPARATING PRECIPITATES FROM LIQUIDBLOOD CONSTITUENTS Filed June 24, 1959 4 Sheets-Sheet 1 INVEN TOR.GEO/P65 M ////1/ Bax/ 04,444,

July 2, 1963 c; N HElN 3 096,283

9 CONTAINER FOR BLOOD AND MACHINE FOR SEPARATING PRECIPITATES FROMLIQUID BLOOD CONSTITUENTS Filed June 24, 1959 4 Sheets-Sheet 2 FIG. 2

INVENTOR. f 650%,; A/- AE/A/ BY a D July 2,, 1963 G. N. CONTAINER FORBLOOD AND HEIN MACHINE FOR SEPARATI PRECIPITATES FROM LIQUID BLOODCONSTITUENTS Filed June 24, 1959 4 Sheets-Sheet 3 July 2., 1963 G. N.HEIN 3,096,283

CONTAINER FOR BLOOD AND MACHINE FOR SEPARATING PRECIPITATES FROM LIQUIDBLOOD CONSTITUENTS Filed June 24, 1959 4 Sheets-Sheet 4 FIG. 5

FIG. 6

IN V EN T 0R. GEOPE /V- #E/A/ United States Patent Oiiice ,i 2,

3,tl96,283 CONTAINER FQR BLQOD AND MACI-IENE lifiR SEPARATBNGPRECEPITATES FROM LIQUED BLOOD CONSTITUENTS George N. Hein, San Carlos,Calif, assignor to Becton,

Dickinson and (Iompany, Rutherford, Ni, 21 corporation of New JerseyFiled June 24, 1959, Ser. No. 822,561 Claims; (Cl.- 2332tl) Thisinvention relates to a functionally and structurally improved receptacleand machine which, when properly used in association with each other,will substantially completely separate precipitates in blood from theliquid plasma or serum.

It is an object of the invention to teach a novel machine and receptaclefor use therewith for separating whole blood into its constituents in amanner such that the remaining liquid (whether plasma or serum) will beclear and in effect free from solids.

A further object is that of teaching an apparatus and receptacle for usetherewith whereby these solids will be in turn subdivided in a mannersuch that white cells, red cells, platelets, fats, etc. may also beseparated or stratified with respect to each other.

Still another object is that of furnishing a receptacle suitable for thereception, storage and treatment of blood, and in which, afterseparation, the clear liquid serum and plasma may readily be used; thesolid constituents being subject to ready. examination and analysis,where such a step is to be resorted to. 7 An additional object is thatof furnishing a machine of relatively simple design and with which thereceptacle may readily be associated in accomplishing such separation.

With these and other objects in mind, reference is had to the attachedsheets of drawings illustrating practical embodiments of the invention,and in which:

FIG. 1 is a fragmentary side elevation of one form of the apparatus aswell as the receptacle for use in connection with the same, the partsbeing separated so that their relationship may more readily bevisualized;

FIG. 2 is a sectionalside view showing the parts in assembledrelationship and in a condition of rest;

FIG. 3 is a view similar to FIG. 2, illustrating the parts of theassembly in diiferent positions and also showing the mechanism in acondition of rest;

FIG. 4 is a sectional side view of one improved form of container forthe blood;

FIG. 5 is a sectional side view of an alternative form of operating headto thatillustrated in FIGS. 1, 2 and v3;

FIG. 6 is a similar view of afurther form of operating head; and

FIG. 7 shows an assembly for mounting a receptacle of the present typeand by'rneans of which that receptacle maybe collapsed or expanded.

Referring primarily to FIG. 1, the numeral 10 indicates a ring-shapedelement forming a part of the machine and which overlies a bowl 11 to besecured against movement with respect thereto by inter-engagingscrewthreads 12 formed respectively on the outer face of the bowl and theinner face of ring 10. Below bowl 11 an actuator ring 13 is disposed andhas extending from it asuitable number 'of handles 14. This ring isinternally threaded and mounted upon the thread 16 of a cup member, inturn supported above a motor casing 19. Extending through the latteris'a hollow tube 20. Conveniently below the motor casing, avtubularextension 21 is provided. Into the latterthere extends a screw-threadedstem 22 terminating in an actuating portion 23.

. As'also shown in this viewand FIG. 2, a blood receptaclesuitable forassociation with the machine is present.

That receptacle is conveniently formed of clear plastic, such as vinyl.As illustrated, it will include a pan-shaped base portion 24, abovewhich there is disposed an upper portion 25. That upper portion may ineffect include an inverted pan-shaped structure, but in any'event, it isprovided with a central opening conveniently defined by an upstandingflange 26, closed by a headed stopper 27, preferably of rubber, havingperforable diaphragm portions 23 which may be penetrated by a cannula.The base part 24 and upper part 25 of the receptacle are coupled by anannulus '28, preferably integral therewith. In many instances it will bepreferred to make the upper part of a material, or of sufficient gauge,so that it will be relatively rigid. Both the base 24 and part 28 may berelatively flexible.

In FIG. 2, in which the interior of the assembly has been illustrated,it will be understood that as shown, the flexible plastic receptacle maybe provided with a cap 2? of aluminum or other suitable material, whichwill serve to retain stopper 27 against displacement from the neckportion 26 of the receptacle. The ring it? has its underface channeled,as indicated at 39, so as to receive part of the rim portion or annulus23 of the receptacle. Similarly, the upper inner edge zone of bowl 11may be recessed, as at 31, to accommodate part of this receptacleportion. Ring ltl is downwardly and inwardly inclined so as to provideat 32 a clamp ledge or zone. A cooperating clamping zone 33 forms a partof a supporting and manipulating member 34 within bowl 11. interposedbetween the supporting and clamping member 34 and the inner face of thebowl is a bezel 35 provided with an inwardly extending portion 35. Theupper edge of this bezel, which functions as an expressing member, is inline with the lower central zone of annulus 28 when the receptacle is inposition. The pins 18 extend through packings such as O-rings in thebase of bowl 11 and engage the inwardly extending bezel portion 26. Ifdesired, the upper portion 25 of the receptacle may be overlain by asupport 37 of frustroconical shape and of any desired material, such asmetal.

Secured to bowl 11 by, for example, a screw-threaded connection is ablock 3% which provides in its upperv face a cylinder slidablysupporting a piston 4d. The skirt of the latter may slidably engage acentrally disposed projecting portion 41 integral with or extending fromthe support and clamp 34. The tube 20 may either provide the shaft forthe motor disposed within casing 19, (FIG. 1), or else be connected sothat it will rotate in unison with that shaft. This tube has a bore 42extending throughout its length. Adjacent the lower end of the tube, thebore is conveniently enlarged to furnish a cylinder within which apiston or plunger 43 is slidably disposed. That plunger is projectableand retractable by securing the inner end of the stem 22 to a cup 44,which supports a bearing 45 carrying a plate 46. The lower end of theplunger is coupled with that plate. Therefore, as stem 22 is projectedand retracted, the plunger will be correspondingly moved.

Any suitable number of bearings of the type indicated at 47 may encircletube or shaft 29 to rotatably support the latter. Also, a thrust bearingor bearings (not shown) may be provided. A further bearing 43 may haveone of its raceways secured to the actuating ring 13'. Its oppositeraceway bears against plate 15. It is apparent that as the ring orcollar is rotated, and due to the engagement of its bore threads withthread 16 of cup 17, that collar will be elevated or lowered, accordingto the directon of rotation. As it elevates, it will cause pins 18 tobear against flange 36 of bezel ring 35 to project the latter.

Access may be gained to the interior of annulus 28 even while the latteris in association with the machine.

If this result is desired, ring may be provided with one or moreopenings in its upper face. These openings are sealed by stoppers 4 ofthe puncture type and which are preferably formed of rubber. Thestoppers will overlie the precipitate chamber provided by the annulus.Therefore, a cannula in the form of a hollow needle, as at 50 (FIG. 3),may be caused to puncture a stopper 4-9, so that the inner end of theneedle enters the interior of the ring portion. Obviously, as the needleis withdrawn, the stopper will reestablish the seal. The parts may be soconstructed that renewal of the stopper or stoppers may be effected whennecessary.

A preferred procedure would involve dismounting ring 10 from bowl 11 anddisposing in proper position within the latter a receptacle such as24-25. This receptacle either would contain whole blood, or else mightreceive it after the reapplication of ring 19 to bowl 11, by, forexample, employing hollow needles for filling and venting purposes andforcing the points of those needles through the properdiaphragm portion28. If before processing, the blood was mixed with an anticoagulantsolution, the resultant material, after completion of the operation,would be grouped on the one hand in the form of a clear plasma filtrateliquid, and on the other hand in the form of solids. The latter wouldconsist of white cells, red cells, platelets, etc. If the blood had notbeen mixed with anti-coagulant prior to the practice of the presentmethod, the resultant liquidafter processingwould be a clear serumfiltrate.

With the ring applied to the bowl, the receptacle will be properlysupported by the mounting and clamp member 34. It will be retainedagainst turning with respect to the rotor assembly by having itsperiphery clamped between the element 10 and bowl member 11. Itsprecipitate chamber, as defined by the annulus 28, will be housed andsupported by the recessed surfaces incorporated in ring 10, theperipheral portion of bowl 11 and the adjacent portions of members 35and 34.

In any event, with the parts properly disposed and plunger 43 and pins18 retracted, the precipitate chamber 23 will be in fully distendedposition. Also, the inner edge zones of that chamber, which continue inthe form of parts 24 and 25, will be spaced in lines with the clampingportions 32 and 33. Such spacing may be on the order of .020". The motorwhich serves to rotate shaft or tube 20 will now be energized. As itoperates, it may cause a turning of that shaft at a speed of around10,000 rpm. With centrifugal force thus created, the solids or othercomponents of high specific gravity within the whole blood will bethrown outwardly and will pass into the annulus 28. This will leavewithin the main chamber of the receptacle, as defined by parts 24 and25, a clear liquid free from solids. While the parts continue to rotateat high speed, any excess liquid unnecessarily deposited within theprecipitate chamber may be returned to the main body of the receptacle.This is achieved by grasping handles 14 and turning the actuating ring13. With such turning in a proper direction, that ring will shift towardbowl 1-1. So shifted, pins 18 will engage flange 36 of bezel 35 to movethe latter from the position shown in FIG. 2 to that illustrated in FIG.3. This action may be continued until substantially all serum or plasmahas been displaced inwardly from chamber 28 through the annular spaceexisting between clamping portions 32 and 33.

Now, by actuating stem 22, plunger 43 will be projected. As shown,O-rings are provided in association with the liquid control system ofthe apparatus. Therefore, with liquid, such as oil within tube 20, itwill be forced up through the cylinder within which piston 45 rides, andso through bore 42 into the cylinder formed in block 39. Within thelatter, it will serve to shift piston 40 toward the receptacle 2425. Soshifting, it will move from the position shown in FIG. 2 to that shownin FIG. 3. Under these circumstances, its skirt will engage theunderface of the supporting and clamping member 34 and elevate thelatter to thus close the gap between sealing or clamping portions 32-33.Therefore, the chamber defined within annulus 28 will be completelysealed from the main body of the receptacle, and the solids within thatchamber will be isolated from the liquid. If at this time it is desiredto withdraw samples of the solids, this may be done without removing thecontainer from the machine, by simply causing a hollow needle toperforate the stopper or stoppers 4?. Of course, prior to suchprocedure, rotation of the parts will have been interrupted.

It is preferred that the motor within casing 19 be subject to control sothat it can rotate at relatively slow speeds. A preferred method ofprocedure involves such a rotation with a receptacle in position withinthe ring and bowl. That receptacle would not be provided with a sealingcap, and in fact might not include a pouring neck or flange 26. Rather,the upper end of the receptacle would simply present an opening throughwhich oxalated blood could be poured or passed into the interior of thereceptacle. Now the speed of rotation is gradually increased up toaround 10,000 rpm, with which a centrifugal force of not less than twothousand times gravity may be developed. This will minimize hemolysis.The plasma will quickly become clear. After sealing of the precipitatechamber has been effected, then that seal should be maintained until theplasma or serum has been removed from the container.

Thus, it will be understood that the present invention offers a radicalimprovement over procedures as heretofore practiced. One such procedureinvolves the placing of the whole blood in a bottle or other receptacleand permitting it to stand for three or four hours. Under thesecircumstances, the majority of the solids will settle to the bottom ofthe receptacle. Such a procedure does not, of course, compact the cells,and produces a plasma or sen-um which will still retain many solids insuspension. Also, the plasma or serum must be Withdrawn withoutdisturbing the solids which have settled to the bottom.

With the other heretofore accepted method, suitable receptacles are usedto receive the blood, and rotation is effected at a speed ofapproximately 2000 r.p.m. Under these conditions, the precipitates areforced to the bottom of the vessel. This force, however, is. notsufficient to remove all solids from the plasma or serum. This isespecially true in that when the centrifuge is once stopped, some of thesolids will again mix with the filtrate. At best, the problem ofremoving that filtrate is a diflicult one, and solids again remain insuspension within it.

One preferred form of container has been generally illustrated in FIG.4. In that view it will be seen this unit involves an upper section 51,preferably in the form of a truncated cone, and having a central opening52 through which liquids may be introduced or withdrawn. A base section53 corresponds to section 51, except that it is imperforate. Bothsections terminate in peripheral portions providing in aggregate anannulus 54, and may have their outer edge zones sealed in face-to-facecontact, as indicated at 55. It is apparent that the receptacle mighttake various other alternative forms, but the two foregoing examples, inaddition to those of FIGS. 5 and 6, will be adequate for the purpose ofvisualizing the range of these forms.

A bowl assembly as shown in FIG. 5 may be resorted to, in which a ring51' is provided corresponding to the ring 10 heretofore described. Also,a bowl 52', similar to bowl 11, has screw-threaded connection therewith.Within this bowl, a support and clamping member 53 is disposed. The baseof the bowl conveniently includes an extension 54 formed with sockets55'. Also, set screws 56 are carried by the bowl, and when projected,bear against the underface of supporting member 53'. Thus, after theparts have been rotated and the Solids 5. separated'fromthe liquid, theclamping member 53' may be shifted by piston 40- (FIG. 2). So projected,its clamping surface 57 will be moved toward thecorresponding surface 58of ringSl' to seal the precipitate chamber and thus isolate the solidswithin the same. When rotation has ceased, set screws'56may be projectedto maintain clamping pressure, if the bowl assembly is to be removedfrom the machine for use. Sockets 55' receive the ends of a bail forcarrying the container.

In FIG. 6 a container 60' has been shown to provide a bowl assemblycorresponding. generally to that illustrated in FIG. 4. A ring 61 hasscrew-threaded connection with a bowl 62. The base of the latter isformed with openings through which rods 63 slidably project; The outeror upper ends of the rods bear against a bezel 64. The latter encirclesa clamping and supporting member 65. If desired, a common ring 66 maysupport all the posts or rods 63, so that they will be projected as aunit; Ring 61 may be formed with openings 67 corresponding to thoseheretofore described and within which the preferredstoppers 49 aredisposed.

A device such as is illustrated in FIG. 6 is especially valuable whenused in laboratory work. It will usually have a capacity of from 4 to 10cc. The volume of the main chamber of the container 60'may, for example,be 6 cc., and the precipitate-chamber, as defined by the annulus, inexpanded condition conveniently involves cc. When the bezel- 64 hasbeenprojected, thecapacity of this solid-receiving chamber isconveniently reduced to 2 cc. or less.

As in FIG. 7, an apparatus is furnished with which the receptacle may beassociated after its removal from the centrifuge. This apparatus willassure a ready collapse or expansion of the container 68. While no clamphas been shown in association with the latter for the purpose of sealingthe precipitate-receiving chamber of the container, it will beunderstood that such a seal may be associated therewith or incorporatedtherein by any suitable expedient, as a-fore suggested. Of course, inmany instances, and under conditions of filling, no seal will benecessary. In any event, a ring 69 may bear against the extended portion70 of the receptacle. This extended portion may incorporate theheat-sealed zone of the container which maintains the sections againstdisplacement with respect to each other. Preferably havingscrew-threaded attachment to ring 69 is a bowl 71. From the latter, aconduit 72 extends through to a suitable apparatus (not shown) wherebyfluids under pressure may be introduced, or a condition of vacuum may becreated within the space between bowl 71 and the container. Withpressure introduced into that space, the base of the container will flexupwardly, as shown in full lines. With a condition of less thanatmospheric pressure, the base will flex outwardly, as indicated indot-and-dash lines. Thus, the container may have its contents expelled,or else an aspiraring action may be resorted to which will fill thecontainer with a desired liquid.

To briefly recapitulate the sequence of operations as heretoforetraversed in connection with FIGS. 1, 2 and 3, it will be understoodthat after the receptacle is associated with the head of the machine asdefined by the ring 10 and bowl 11 thereof, the auxiliary or annularportion of the receptacle has its interior in communication with themain part of the cavity defined by the receptacle. Through thelimited-area passage connecting these cavities, the solids will pass asthe head rotates at high speed, to be retained within the annulus 28. Ifa structure such as bezel 35 is employed, then it is feasible todisplace any excess serum or plasma deposited within the annulus 28 backinto the main cavity of the receptacle. In any event, when theseparation of the components has been effected within the limits of themachine design involved, the cooperating clamping portions 32 and 33will be caused to seal off one cavity from the other, to thus 6 entrapthe different material in those cavities. The difference between themolecular weights of the substances will assure that all the solids arewithin the annulus, while the serum or plasma is contained within themain body of the receptacle.

While the receptacle in its upper, intermediate and lower sectionsshould include a certain amount of flex ibility, it is preferred that atleast certain of these parts be sufiiciently firm to embody stability inthe receptacle as a whole. Also, it is preferred that the receptacle beprovided with a seal of the type shown at 26, 27, 28' and 29, ratherthan have a permanently open upper face. The attachment of ring 10 tobowl 11 may be effected in-many different manners to expose the cavitieswithin the head. It is apparent that while the present invention is ofgreat value when applied to the separation of blood components, itmay beadvantageously employed for the separation of materials having differentspecific gravitiesi In many instances it will be desirable to employliquid; as indicated in FIGS. 2 and 3, within bowl 11 for the purpose ofassuring :a proper balance or equilibrium in the assembly. However, theapparatus will function entirely satisfactorily in the absence of thatliquid, if the speed of operation isheld within design limitations.

Thus, among others, the several objects of theihvention :as specificallyaforenoted are achieved. It is apparent that the construction of themachine and receptacle may be revised in numerous respects withoutdeparting from the spirit of the invention as defined by the claims.

I claim:

1. Apparatus for use in separating materials into components ofrelatively higher and relatively lower specific gravity which comprises:a drive shaft and IE1 motor for causing the rotation thereof, a rotorhead operatively connected to the drive shaft to be rotated thereby andformed With a circular recess concentric with the center of rotation, aseparate removable liner in the recess in the rotor head in the form ofa hollow circular body having upper and lower walls of sheet materialspaced from each other to provide a central chamber and connectedtogether around their peripheries to provide an annular chamber closedaround the outer edge and communicating with the central chamber at itsinner edge, said walls having annular confronting sealing zones betweenthe two chambers, at least one of the walls being flexible so thatsealing zones can be brought into sealing engagement with each other,said rotor having clamping means spaced inwardly from the periphery ofthe recess in registry with the sealing zones of the liner to clamp saidsealing zones into sealing engagement with each other, means forcompressing the flexible wall of said liner around the annular chamberwhile the rotor head is rotating to express some or" the materials fromthe annular chamber into the central chamber and means for thereafteroperating said clamping means while said rotor head is rotating to causesaid sealing zones to have sealing engagement and thereby seal off thematerials of relatively higher specific gravity in the annular chamberfrom the materials of relatively lower specific gravity in the centralchamber.

' 2. Apparatus for use in separating materials into com ponents ofrelatively higher and relatively lower specific gravity comprising adrive shaft and a motor for causing the rotation thereof, a rotor headoperatively connected to the drive shaft to be rotated thereby andformed with a circular recess concentric with the center of rotation, aseparate removable liner in the recess in the rotor head in the form ofa hollow circular body having upper and lower walls of sheet materialspaced from each other to provide a central chamber and connectedtogether around their peripheries to define an annular chamber closedaround the outer edge and communicating with the central chamber at itsinner edge, said walls having .annular confronting sealing zones betweenthe two chambers,

at least one of the walls being flexible so that sealing zones can bebrought into sealing engagement with each other, said head havingclamping means space-d inwardly from the periphery of the recess inregistry with the sealing zones of the liner to clamp said sealing zonesinto sealing engagement with each other, and means for operating saidclamping means While said rotor head is rotating to cause said sealingzones to have sealing en gagernent and thereby sealing off materials ofrelatively higher specific gravity in the annular chamber from materialsof relatively lower specific gravity in the central chamber.

3. A receptacle for use as a disposable liner in a centrifuge rotor ofthe type which during rotation seals off one annular area thereof tosegregate material of relatively higher specific gravity from materialof relatively lower specific gravity, said receptacle comprising: ahollow circular body having an upper wall and a lower wall made of sheetmaterial spaced from each other to provide a central chamber and beingconnected together continuously around the periphery of the body toprovide an annular chamber extending completely around the body, saidannular chamber being enclosed around its outer edge and communicatingwith the central chamber along its inner edge, said walls having annularsealing zones extending around said body between said chambers inconfronting relationship with each other, with at least one of saidWalls being flexible so that the sealing zones can 8, be brought intosealing engagement with each other to seal off the annular chamber fromthe central chamber and said upper wall being provided with a centralportion through which materials separated in the receptacle can bewithdrawn.

4. A receptacle for use as a disposable liner in a centrifuge rotor ofthe type which during rotation seals ofi one annular area thereof tosegregate material of relatively higher specific gravity from materialof lower specific gravity as set forth in claim 3 in which the lowerwall of the receptacle body is flexible and the upper wall is relativelymore rigid.

5. The invention in accordance with claim 3 wherein access means are onsaid receptacle at said annular chamber for providing access to theannular chamber.

References Cited in the file of this patent UNITED STATES PATENTS2,023,762 Fawcett Dec. 10, 1935 2,272,675 Knudsen Feb. 10, 19422,656,263 Larsen Oct. 20, 1953 2,883,103 Whitehead et al Apr. 21, 19592,898,037 Dega Aug. 4, 1959 FOREIGN PATENTS 66,298 Sweden Oct. 30, 1928252,907 Germany Oct. 28, 1912 971,978 France Aug. 23, 1950

1. APPARATUS FOR USE IN SEPARATING MATERIALS INTO COMPONENTS OFRELATIVELY HIGHER AND RELATIVELY LOWER SPECIFIC GRAVITY WHICH COMPRISES:A DRIVE SHAFT AND A MOTOR FOR CAUSING THE ROTATION THEREOF, A ROTOR HEADOPERATIVELY CONNECTED TO THE DRIVE SHAFT TO BE ROTATED THEREBY ANDFORMED WITH A CIRCULAR RECESS CONCENTRIC WITH THE CENTER OF ROTATION, ASEPARATE REMOVABLE LINER IN THE RECESS IN THE ROTOR HEAD IN THE DORM OFA HOLLOW CIRCULAR BODY HAVING UPPER AND LOWER WALLS OF SHEET MATERIALSPACED FROM EACH OTHER TO PROVIDE A CENTRAL CHAMBER AND CONNECTEDTOGETHER AROUND THEIR PERIPHERIES TO PROVIDE AN ANNULAR CHAMBER CLOSEDAROUND THE OUTER EDGE AND COMMUNICATING WITH THE CENTRAL CHAMBER AT ITSINNER EDGE, SAID WALLS HAVING ANNULAR CONFRONTING SEALING ZONES BETWEENTHE TWO CHAMBERS, AT LEAST ONE OF THE WALLS BEING FLEXIBLE SO THATSEALING ZONES CAN BE BROUGHT INTO SEALING ENGAGEMENT WITH EACH OTHER,SAID ROTOR HAVING CLAMPING MEANS SPACED INWARDLY FROM THE PERIPHERY OFTHE RECESS IN REGISTRY WITH THE SEALING ZONES OF THE LINER TO CLAMP SAIDSEALING ZONES INTO SEALING ENGAGMENT WITH EACH OTHER, MEANS FORCOMPRESSING THE FLEXIBLE WALL OF SAID LINER AROUND THE ANNULAR CHAMBERWHILE THE ROTOR HEAD IS ROTATING TO EXPRESS SOME OF THE MATERIALS FROMTHE ANNULAR CHAMBER INTO THE CENTRAL CHAMBER AND MEANS FOR THEREAFTEROPERATING SAID CLAMPING MEANS WHILE SAID ROTOR HEAD IS ROTATING TO CAUSESAID SEALING ZONES TO HAVE SEALING ENGAGEMENT AND THEREBY SEAL OFF THEMATERIALS OF RELATIVELY HIGHER SPECIFIC GRAVITY IN THE ANNULAR CHAMBERFROM THE MATERIALS OF RELATIVELY LOWER SPECIFIC GRAVITY IN THE CENTRALCHAMBER.